The present invention generally relates to control systems. More particularly, the present invention relates to control systems suitable for controlling movement of an aircraft rudder.
An aircraft often includes one or more control systems designed to control the aircraft rudder position during flight. Such systems are generally configured to manipulate the rudder position to (1) stabilize the aircraft during flight or (2) provide directional compensation when one or more aircraft engines loose power.
Stabilization or yaw damping control systems are generally designed to manipulate the aircraft rudder position to compensate for wind gusts, turbulence, phenomena such as Dutch roll, and the like. Typical yaw damping control systems include a motor or apparatus to move the rudder and a feedback control loop designed to control the motor and thus the rudder position.
Directional compensation systems are designed to facilitate directional control of the aircraft when the aircraft looses all or most of the power from one or more engines. For example, directional compensation systems are often employed to reduce an amount of force a pilot is required to apply to a rudder control system when one engine fails on a dual engine aircraft. An amount of force reduction that the compensation system provides may vary, depending on various factors such as the differential force provided by one or more engines on the aircraft, the type of aircraft, and aircraft manufacturer preferences. For example, an aircraft with relatively small engine thrust may not require any directional compensation, while aircraft with relatively large engine thrust would generally include a compensation system configured to facilitate rudder position, such that no more than about 150 pounds force is required by a pilot to maneuver the rudder to compensate for the engine power loss.
Aircraft including both stabilization and directional compensation systems generally include separate motors and control devices dedicated to each system. Although dedicating motors and control devices for each system may allow for relatively easy design of each of the respective systems, using two separate systems may be problematic in several regards. For example, aircraft including two separate rudder control systems generally operate such that only one rudder control system can function at any given time. Thus, the stabilization system generally does not operate when the directional compensation system is employed. Accordingly, improved aircraft rudder control systems that simultaneously provide both stabilization and directional compensation rudder control are desired.
Another problem associated with aircraft including dedicated rudder control systems is that such aircraft generally include superfluous control devices and/or rudder movement motors. Accordingly, improved rudder control systems which use a single control device and a single motor to provide both yaw damping stabilization and directional compensation control are desired.
The present invention provides improved apparatus for controlling aircraft rudder movement and position. The way in which the present invention addresses the deficiencies of now-known rudder control systems is discussed in greater detail below. However, in general, the present invention provides a single system suitable for simultaneously providing yaw-damping stability and directional-compensation rudder control.
In accordance with one exemplary embodiment of the present invention, a rudder control system includes a yaw damping stability portion integrated with a directional compensation portion. The integrated system includes a yaw damping command signal generator, a bias command signal generator, at least one summing junction configured to combine signals from the yaw damping and bias command signal generators, and a motor configured to receive the summed yaw damping and bias command signals and move an aircraft rudder in response to the summed signal.
In accordance with an exemplary embodiment of the present invention, the control system includes a bias command feed forward path configured to transmit a signal representative of engine thrust differential (difference in thrust between two or more engines on an aircraft) to the motor. In accordance with one aspect of this embodiment, the feed forward path includes a wash out filter and a lag filter. In accordance with another aspect of this embodiment, the feed bias command forward loop path includes one or more gain devices to facilitate turning of the control loop.
In accordance with a further embodiment of the present invention, the aircraft rudder control system includes a motor rate feedback loop configured to provide negative feedback to the system to reduce damping motion speed.
In accordance with another embodiment of the present invention, the aircraft rudder control system includes a motor current feedback path configured to a feedback signal based on motor load.
In accordance with yet another embodiment of the present invention, the bias command signal is transmitted through a feedback path including a signal filter configured to diminish the input bias command signal over time.
In accordance with a further exemplary embodiment of the present invention, the control system includes a second motor current feedback path configured to facilitate fine tuning or the rudder control motor.